The present invention relates to a determining method of a control condition for a thermal (heat) processing system that carries out a thermal process for an object to be processed such as a substrate. In particular, the present invention relates to a determining method of a control condition of a thermal processing system for forming a uniform film on a substrate.
For a semiconductor-device manufacturing process, as one of units that carry out a heat process to a semiconductor wafer (hereafter, a wafer) as a substrate, there is a vertical type of thermal processing unit that carries out a batch process. The unit holds many wafers in a tier-like manner with a wafer holder, which is called a wafer boat or the like, and transfers the holder into a vertical heat-processing furnace to conduct a CVD (Chemical Vapor Deposition) process or an oxidation process.
When a wafer undergoes a heat process by means of the thermal processing unit, ununiformity may arise in a condition of the heat process within a surface of the same wafer or between a plurality of wafers. As a result, unevenness in thickness distribution of a film formed by the heat process may be generated within a surface of the same processed wafer or between a plurality of processed wafers.
It is ideal that there is a uniform state in the thermal processing unit in order to uniformly conduct a heat process to a plurality of wafers. However, it is difficult to always make a state in the thermal processing unit uniform with respect to both time and space.
Therefore, it is necessary to precisely control the thermal processing unit in order to conduct a heat process to a plurality of wafers under a more uniform condition.
The present invention has been made to solve such a problem and it is an object of the present invention to provide a method of determining a control condition for uniformly conducting a heat process to a plurality of wafers by means of a thermal processing unit.
In addition, in a conventional heat processing unit, a stabilization time is required to make a temperature of a substrate stable, for a purpose of conducting a heat process uniformly within a surface of the substrate. Thus, it takes a long time to conduct the heat process by the stabilization time, so that the throughput is deteriorated.
The present invention has been made to solve such a problem and it is an object of the present invention to provide a heat processing unit that can carry out a heat process uniformly within a surface of a substrate even if the stabilization time is shortened.
The present invention is a method of determining a set temperature profile for a method of controlling respective substrate temperatures of a plurality of groups in accordance with respective corresponding set temperature profiles, in a method of heat processing a plurality of substrates that are classified into the plurality of groups, the method of determining a set temperature profile comprising: a first heat processing step of controlling respective substrate temperatures of a plurality of groups in accordance with respective predetermined provisional set temperature profiles for first-batch substrates that are classified into the plurality of groups, and of introducing a process gas to conduct a heat process to form films on the substrates; a first film-thickness measuring step of measuring a thickness of the films formed on the substrates; and a first set-temperature-profile amending step of respectively amending the provisional set temperature profiles based on the measured thickness, in such a manner that a thickness of films formed during a heat process is substantially the same between the plurality of groups; wherein, in the first heat processing step, the provisional set temperature profiles are profiles whose set temperatures change as time passes.
Thickness distribution of the films between the substrates can be made uniform, by amending the provisional set temperature profiles that are profiles whose set temperatures change as time passes.
It is preferable to maintain substantially the same patterns except components of constant terms (offsets) when amending the provisional set temperature profiles. In the case, it becomes difficult for thickness distribution within a substrate to change between before and after the amendment.
Preferably, in the first heat processing step, set temperatures of the provisional set temperature profiles have a substantially constant gradient with respect to time. Steepness of the gradient is a factor that determines temperature distribution within a surface of the substrate. By making the gradient constant, temperature distribution during the heat process and hence distribution of film-forming rate can be made constant with respect to time.
Preferably, in the first film-thickness measuring step, for at least one substrate in each of the plurality of groups, film thickness is measured at a plurality of points of each substrate, and an average of the measured values is obtained as a film thickness of the substrate.
Preferably, in the first set-temperature-profile amending step, averages of ideal set temperatures to be amended are calculated based on a thickness-temperature dependant relationship between the substrate temperatures and the film thickness, and the provisional set temperature profiles are amended based on the averages.
Averages of the set temperatures are factors that correspond to averages of film-growing rates. Thus, it is effective to make film-thickness distribution uniform based on the averages of the set temperatures.
The thickness-temperature dependant relationship can be represented for example by a thickness-temperature coefficient. In addition, as a thickness-temperature dependant relationship, a theoretical equation can be used. Values obtained from experiments can be also used.
Preferably, the present invention is a method of determining a set temperature profile according to claim 1, further comprising after the first set-temperature-profile amending step: a second heat processing step of controlling the respective substrate temperatures of the plurality of groups in accordance with respective amended first set temperature profiles for second-batch substrates that are classified into the plurality of groups, and of introducing a process gas to conduct a heat process to form films on the substrates; a second film-thickness measuring step of measuring a thickness of the films formed on the substrates; and a second set-temperature-profile amending step of respectively amending the first set temperature profiles based on the measured thickness, in such a manner that a thickness of films formed during a heat process is substantially the same between the plurality of groups.
Preferably, in the second set-temperature-profile amending step, averages of ideal set temperatures to be amended are calculated based on a thickness-temperature dependant relationship between the substrate temperatures and the film thickness, and the first set temperature profiles are amended based on the averages.
Preferably, in the second set-temperature-profile amending step, the thickness-temperature dependant relationship between the substrate temperatures and the film thickness is amended based on: averages in time of the provisional set temperature profiles during the first heat processing step, film thickness of the films on the first-batch substrates, averages in time of the first set temperature profiles during the second heat processing step, and film thickness of the films on the second-batch substrates.
Preferably, the second heat processing step, the second film-thickness measuring step and the second set-temperature-profile amending step are repeated at least twice in order thereof.
In addition, the present invention is a method of determining a set temperature profile for a method of controlling respective substrate temperatures of a plurality of groups in accordance with respective corresponding set temperature profiles, in a method of heat processing a plurality of substrates that are classified into the plurality of groups, the method of determining a set temperature profile comprising: a first set-temperature-profile determining step of determining first set temperature profiles, each of which is set for each of a plurality of groups of substrates, in accordance with which films of substantially the same thickness between the plurality of groups are formed on the substrates when a process gas is introduced to conduct a heat process, and whose set temperatures don""t change as time passes during the heat process; a second set-temperature-profile determining step of determining second set temperature profiles, each of which is set for each of the plurality of groups of the substrates by amending each first set temperature profile, in accordance with which a film of substantially the same thickness is formed on each of the substrates when a process gas is introduced to conduct a heat process, and whose set temperatures change as time passes during the heat process; and a third set-temperature-profile determining step of determining third set temperature profiles, each of which is set for each of the plurality of groups of the substrates by amending each second set temperature profile, in accordance with which films of substantially the same thickness between the plurality of groups are formed on the substrates when a process gas is introduced to conduct a heat process, and whose set temperatures change as time passes during the heat process.
According to the invention, a control condition that can obtain good film-thickness distribution with respect to both between the plurality of groups of the substrates and within a surface of each of the substrates can be easily determined.
Preferably, the first set-temperature-profile determining step includes: a first heat processing step of controlling respective substrate temperatures of the plurality of groups in accordance with respective predetermined provisional set temperature profiles for first-batch substrates that are classified into the plurality of groups, and of introducing a process gas to conduct a heat process to form films on the substrates; a first film-thickness measuring step of measuring a thickness of the films formed on the substrates; and a first set-temperature-profile amending step of calculating ideal constant set temperatures based on the measured thickness, in such a manner that a thickness of films formed during a heat process is substantially the same between the plurality of groups, and of respectively amending the provisional set temperature profiles based on the ideal constant set temperatures.
In the case, thickness distribution of the films on the substrates can be made uniform between the plurality of groups of the substrates.
Preferably, in the first set-temperature-profile amending step, the ideal constant set temperatures are calculated based on a thickness-temperature dependant relationship between the substrate temperatures and the film thickness.
As the thickness-temperature dependant relationship, a theoretical equation can be used, and also values obtained from experiments can be used.
Preferably, in the first film-thickness measuring step, for at least one substrate in each of the plurality of groups, film thickness is measured at a plurality of points of each substrate, and an average of the measured values is obtained as a film thickness of the substrate.
In addition, preferably, the first set-temperature-profile determining step includes after the first set-temperature-profile amending step: a second heat processing step of controlling the respective substrate temperatures of the plurality of groups in accordance with respective amended provisional set temperature profiles for second-batch substrates that are classified into the plurality of groups, and of introducing a process gas to conduct a heat process to form films on the substrates; a second film-thickness measuring step of measuring a thickness of the films formed on the substrates; and a second set-temperature-profile amending step of calculating again ideal constant set temperatures based on the measured thickness, in such a manner that a thickness of films formed during a heat process is substantially the same between the plurality of groups, and of respectively amending again the amended provisional set temperature profiles based on the ideal constant set temperatures.
Preferably, in the second set-temperature-profile amending step, the ideal constant set temperatures are calculated again based on a thickness-temperature dependant relationship between the substrate temperatures and the film thickness.
Preferably, in the second set-temperature-profile amending step, the thickness-temperature dependant relationship between the substrate temperatures and the film thickness is amended based on: set temperatures of the provisional set temperature profiles during the first heat processing step, film thickness of the films on the first-batch substrates, set temperatures of the amended provisional set temperature profiles during the second heat processing step, and film thickness of the films on the second-batch substrates.
Preferably, the second heat processing step, the second film-thickness measuring step and the second set-temperature-profile amending step are repeated at least twice in order thereof.
Preferably, averages in time of set temperatures of the second set temperature profiles during the heat process are substantially the same as constant set temperatures of the first set temperature profiles during the heat process.
Preferably, set temperatures of the second set temperature profiles during the heat process have a substantially constant gradient with respect to time. Thus, temperature distribution on a surface of the substrate and hence distribution of film-growing rate can be made substantially constant with respect to time.
Preferably, the second set-temperature-profile determining step includes: a third heat processing step of controlling respective substrate temperatures of the plurality of groups in accordance with the respective first set temperature profiles for third-batch substrates that are classified into the plurality of groups, and of introducing a process gas to conduct a heat process to form films on the substrates; a third film-thickness measuring step of measuring a thickness distribution of the films formed on the substrates; and a third set-temperature-profile amending step of respectively amending the first set temperature profiles based on the measured thickness distribution.
In the case, film-thickness distribution can be made uniform within a surface of each of the substrates, while maintaining uniformity in film-thickness distribution between the plurality of groups of the substrates to some extent.
Preferably, the third film-thickness measuring step includes: a step of measuring a film thickness on the substrate near a central portion thereof; and a step of measuring a film thickness on the substrate near a plurality of peripheral portions thereof.
Preferably, the third film-thickness measuring step includes: a step of obtaining the thickness distribution on the substrates as a function of a distance from a substantially center thereof.
Preferably, the function is a function of a square of the distance from the substantially center thereof.
Preferably, the third film-thickness measuring step includes: a step of obtaining the thickness distribution on the substrates as a difference between a film thickness near a central portion thereof and a film thickness near a peripheral portion thereof.
Preferably, in the third set-temperature-profile amending step, a necessary temperature distribution in one substrate that is necessary for forming a film whose thickness is substantially uniform within a surface of the substrate is adapted to be calculated based on a thickness-temperature dependant relationship between the substrate temperatures and the film thickness and the measured thickness distribution.
Since temperature during the heat process is a factor greatly relating to film-growing rate, film-thickness distribution within a surface of each of the substrates can be made uniform, by controlling temperature distribution within the surface of each of the substrates.
As the thickness-temperature dependant relationship, a theoretical equation can be used, and also values obtained from experiments can be used. If averages in time of the set temperatures changing as time passes are used as the temperature, handling is easy.
Preferably, the necessary temperature distribution is represented by a difference between a temperature of the substrate near a central portion thereof and a temperature of the substrate near a peripheral portion thereof.
Preferably, in the third set-temperature-profile amending step, necessary gradients with respect to time of set temperature profiles to be obtained by amended are calculated based on a dependant relationship between gradients with respect to time of set temperature profiles and temperature distribution within the substrate and the necessary temperature distribution, and the first set temperature profiles are adapted to be amended based on the necessary gradients.
Thus, the temperature distribution within the surface of each of the substrates can be suitably controlled, so that the film-thickness distribution within the surface of each of the substrates can be made uniform.
In addition, preferably, the second set-temperature-profile determining step includes after the-third set-temperature-profile amending step: a fourth heat processing step of controlling the respective substrate temperatures of the plurality of groups in accordance with respective amended first set temperature profiles for fourth-batch substrates that are classified into the plurality of groups, and of introducing a process gas to conduct a heat process to form films on the substrates; a fourth film-thickness measuring step of measuring a thickness distribution of the films formed on the substrates; and a fourth set-temperature-pro file amending step of respectively amending again the amended first set temperature profiles based on the measured thickness distribution.
In the case, film-thickness distribution can be adjusted between the plurality of groups of the substrates, while maintaining uniformity in film-thickness distribution within a surface of each of the substrates to some extent.
Preferably, in the fourth set-temperature-profile amending step, a necessary temperature distribution in one substrate that is necessary for forming a film whose thickness is substantially uniform within a surface of the substrate is adapted to be calculated based on a thickness-temperature dependant relationship between the substrate temperatures and the film thickness and the measured thickness distribution.
Preferably, in the fourth set-temperature-profile amending step, the thickness-temperature dependant relationship between the substrate temperatures and the film thickness is amended based on: averages in time of the first set temperature profiles during the third heat processing step, film thickness of the films on the third-batch substrates, averages in time of the amended first set temperature profiles during the fourth heat processing step, and film thickness of the films on the fourth-batch substrates.
Preferably, the fourth heat processing step, the fourth film-thickness measuring step and the fourth set-temperature-profile amending step are repeated at least twice in order thereof.
Preferably, the third set-temperature-profile determining step includes: a fifth heat processing step of controlling respective substrate temperatures of the plurality of groups in accordance with the respective second set temperature profiles for fifth-batch substrates that are classified into the plurality of groups, and of introducing a process gas to conduct a heat process to form films on the substrates; a fifth film-thickness measuring step of measuring a thickness of the films formed on the substrates; and a fifth set-temperature-profile amending step of calculating averages of set temperatures based on the measured thickness, in such a manner that a thickness of films formed during a heat process is substantially the same between the plurality of groups, and of respectively amending the second set temperature profiles based on the averages of set temperatures.
In addition, the present invention is a heat processing unit comprising: a processing chamber in which a substrate is contained; a heater that heats the substrate contained in the processing chamber; a gas-introducing part that introduces a process gas into the processing chamber in order to conduct a heat process to the substrate; and a controller that controls the heater and the gas-introducing part, in accordance with a process recipe including a set temperature profile defining a relationship between a passage of time and a set temperature, in order to conduct the heat process to the substrate, wherein: the set temperature profile is defined in such a manner that, with respect to the substrate during the heat process, both a central-high-temperature state wherein a temperature near a central portion thereof is higher than a temperature near a peripheral portion thereof and a peripheral-high-temperature state wherein a temperature near the peripheral portion thereof is higher than a temperature near the central portion thereof can appear.
According to the invention, during the heat process, there are both the central-high-temperature state wherein a temperature near the central portion of the substrate is higher and the peripheral-high-temperature state wherein a temperature near the peripheral portion thereof is higher. The central-high-temperature state and the peripheral-high-temperature state may cancel out each other, so that the central temperature and the peripheral temperature may approach each other in their averages with respect to time. Thus, even if a stabilization time is shortened, it is easy to uniformly conduct the heat process to a surface of the substrate.
Preferably, the set temperature profile is defined in such a manner that, with respect to the substrate during the heat process, an average in time of the temperature near the central portion thereof is substantially the same as an average in time of the temperature near the peripheral portion thereof. Since the average in time of the central temperature is substantially the same as the average in time of the peripheral temperature, it is easy to secure uniformity of the heat process to the surface of the substrate.
Preferably, the set temperature profile is defined to change as time passes during the heat process.
Preferably, the set temperature profile is defined to change as time passes before the heat process.
In addition, the present invention is a heat processing method of conducting a heat process to a substrate using a heat processing unit including: a processing chamber in which a substrate is contained; a heater that heats the substrate contained in the processing chamber; a gas-introducing part that introduces a process gas into the processing chamber in order to conduct a heat process to the substrate; and a controller that controls the heater and the gas-introducing part, in accordance with a process recipe including a set temperature profile defining a relationship between a passage of time and a set temperature, in order to conduct the heat process to the substrate; the method comprising: a heat processing step of heating the substrate and introducing the process gas into the processing chamber, in accordance with the process recipe, wherein: the heat processing step has: a central-high-temperature step wherein a temperature near a central portion of the substrate is higher than that near a peripheral portion thereof, and a peripheral-high-temperature step wherein a temperature near the peripheral portion of the substrate is higher than that near the central portion thereof.
According to the invention, the central-high-temperature state and the peripheral-high-temperature state may cancel out each other. Thus, even if a stabilization time is shortened, it is easy to secure uniformity of the heat process within a surface of the substrate.
The set temperature profile may be defined to change as time passes, during the heat processing step.
The set temperature profile may be defined to go down as time passes, during the heat processing step. In the case, preferably, the central-high-temperature step is conducted after the peripheral-high-temperature step. Because, if heating of the substrate and heat radiation from the substrate are conducted from the peripheral portion of the substrate, the peripheral temperature of the substrate goes down more rapidly than the central temperature, as the set temperatures go down as time passes.
Alternatively, the set temperature profile may be defined to go up as time passes, during the heat processing step. In the case, preferably, the peripheral-high-temperature step is conducted after the central-high-temperature step. Because, if heating of the substrate and heat radiation from the substrate are conducted from the peripheral portion of the substrate, the peripheral temperature of the substrate goes up more rapidly than the central temperature, as the set temperatures go up as time passes.
Preferably, an average in time of the temperature near the central portion of the substrate is substantially the same as an average in time of the temperature near the peripheral portion thereof, during the heat processing step. This can lead to securing of a uniform heat process within a surface of the substrate.
Preferably, the temperature near the peripheral portion of the substrate is an average of temperatures at a plurality of points near the peripheral portion of the substrate.
Preferably, the process gas is introduced into the processing chamber at a substantially constant density, during the heat processing step. In the case, it is easy to conduct a uniform heat process within a surface of the substrate.
Preferably, the process gas is introduced into the processing chamber under a substantially constant pressure, during the heat processing step. In the case, it is easy to conduct a uniform heat process within a surface of the substrate.
In addition, a heat processing method can further comprise a heating step whose set temperature profile is defined to go up as time passes, before the heat processing step.
In the case, a heat processing method can further comprise a change-in-time set temperature step whose set temperature profile is defined to change as time passes, between the heating step and the heat processing step. Alternatively, a heat processing method can further comprise a constant set temperature step whose set temperature profile is defined not to change as time passes, between the heating step and the heat processing step.
In addition, the present invention is a method of heat processing a substrate, comprising: a heating step of raising both a central temperature near a central portion of the substrate and a peripheral temperature near a peripheral portion of the substrate by heating the substrate by means of a thermal output within a first range; and a heat processing step of forming a film on the substrate while lowering both the central temperature and the peripheral temperature by heating the substrate from a periphery thereof in a process gas atmosphere by means of a thermal output within a second rage, which is smaller than the thermal output within the first range, the heat processing step having a central-high-temperature step wherein the central temperature of the substrate is higher than the peripheral temperature and a peripheral-high-temperature step wherein the peripheral temperature is higher than the central temperature.
According to the invention, even if a stabilization step between the heating step and the heat processing step (film-forming step) is shortened, or even if a stabilization step is not provided, it is easy to secure uniformity of the heat process within a surface of the substrate.
In addition, the present invention is a recording medium in which a process recipe is recorded, the process recipe including a set temperature profile defining a relationship between a passage of time and a set temperature during a heat process, wherein: a heat processing step wherein the substrate is heated and wherein a process gas is introduced into a processing chamber containing the substrate in accordance with the process recipe has: a central-high-temperature step wherein a temperature near a central portion of the substrate is higher than that near a peripheral portion thereof, and a peripheral-high-temperature step wherein a temperature near the peripheral portion of the substrate is higher than that near the central portion thereof.